FastAPI Authentication Tutorial: Credentials, Tokens and Access Decisions
Authentication establishes which identity a request represents. A login flow checks credentials and supplies a mechanism for subsequent requests, such as a bearer token or a session cookie. Protected endpoints then resolve the identity before deciding what it is allowed to do. Password handling, token validation and access rules are separate responsibilities: accepting a well-formed token is insufficient if its signature or expiration has not been checked. Response schemas also need to keep internal credential data out of public output. This topic follows those boundaries so a login example can be understood as part of a complete access-control flow.
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Why Use FastAPI Authentication Tutorial: Credentials, Tokens and Access Decisions
- Separate identity verification from permission decisions
- Verify credentials using appropriate password hashing
- Understand how bearer tokens accompany requests
- Check token validity before trusting identity claims
- Restrict protected actions using server-side authorization rules
Frequently Asked Questions
How does authentication differ from authorization?
Authentication identifies the requester, while authorization decides which actions that identity can perform. A logged-in user is not automatically entitled to read every record, so resource-specific permission checks still belong on the server.
Is a JWT payload encrypted by default?
A signed JWT commonly encodes its payload without encrypting it. The signature supports integrity checking, but readable claims should not contain secrets merely because they are packaged inside a token sent to the client.
Why hash passwords instead of storing their original values?
Password verification does not require retaining the plaintext credential. A suitable password-hashing method produces a stored representation for checking attempts, reducing direct exposure of original passwords if the credential database is disclosed.
What should a protected route verify before using token claims?
The token must satisfy the application's validation rules, including cryptographic verification and applicable expiration or other claim checks. Only then should the route resolve the identity and evaluate permission for the requested operation.
Does CORS protect an API from unauthorized callers?
CORS controls certain cross-origin interactions by browsers. It does not establish a caller's identity or permission, and non-browser clients are not constrained in the same way, so it cannot replace authentication and authorization.